This invention relates generally to an inclination angle adjusting mechanism, in an optical disk apparatus for data recording and reproduction on and from a CD (Compact Disc), DVD (Digital Versatile Disk) or the like, for adjusting the inclination of a spindle motor relative to a chassis so that a rotary shaft of the spindle motor lies parallel to an optical axis of an optical pickup. More specifically, the invention relates to such an inclination angle adjusting mechanism which allows independent adjustment of the inclination angle in a track-widthwise direction and a track-tangential direction and reduces the amount of movement of a turntable upon adjustment.
For storing information in an optical disk or reproducing the information from the optical disk, it is necessary for an optical axis of an optical pickup to pass perpendicularly to a storage surface of the optical disk. For this purpose, a rotary shaft of a spindle motor of an the optical disk apparatus and the optical axis of the optical pickup need to be arranged parallel to each other. However, due to a molding error and/or an assemblage error in a chassis of the optical disk apparatus, the rotary shaft of the spindle motor and the optical axis of the optical pickup maybe arranged somewhat offset from the desired parallel state. Therefore, an inclination angle adjusting mechanism is installed on the chassis so that after completion of assemblage, the spindle motor can be inclined relative to the chassis to thereby place the rotary shaft of the spindle motor parallel to the optical axis of the optical pickup. The inclination angle adjustment is carried out before shipping of the resulting product.
FIGS. 2A-2D hereof show a conventional inclination angle adjusting mechanism. A chassis 10 includes pedestals 12, 14 fixedly disposed thereon. The pedestals 12, 14 have inclined surfaces 12a, 14a on which a motor base 18 with a spindle motor fixedly disposed thereon is placed. Part 18c of the pedestal 18 abuts against an inclined cam surface 37a at an upper end of a cylindrical cam 37 rotatably attached to the chassis 10. A turntable 22 is mounted on a rotary shaft 20 of a spindle motor 16. Screws 24, 26, 28 pass through the motor base 18 and are threaded into the mecha-chassis 10. Around the screws 24, 26, 28, springs 31, 32, 33 are disposed in their compressed states such that their resilient forces press the motor base 18 against the pedestal inclined surfaces 12a, 14a and cam surface 37a. An eccentric cam 27 has an eccentric pin 29 which is engaged in a cam hole 30 of the motor base 18. By turning the eccentric cam 27 in a direction of arrow K with the eccentric pin 29 engaged in the cam hole 30, the motor base 18 is caused to move in a direction of arrow L while ends 18a, 18b of the motor base 18 slide along the inclined surfaces 12a, 14a of the pedestals 12, 14, thereby completing the adjustment of the inclination angle in one direction (track-tangential direction) of the spindle motor 16 relative to the chassis 10. At this time, the pins 25, 27 fixedly secured to the chassis 10 are engaged in recesses 18d, 18d of the motor base 18 thereby inhibiting sliding movement of the motor base 18 in a direction perpendicular to the rotary shaft 20 and to the arrow L. By turning the cylindrical cam 37 in a direction of arrow M, the motor base 18 rotates about an axis N or N'corresponding to its side portions placed in contact with the pedestal inclined surfaces 12, 14, thereby perfecting the adjustment of inclination angle in another direction (truck-widthwise direction).
Japanese Patent Laid-Open Publication No. HEI-8-17135 shows another conventional inclination angle adjusting mechanism as illustrated in FIG. 3 hereof. A turntable 38 is mounted to a rotary shaft 36 of a spindle motor 35 which is fixedly disposed on a motor base 40. The motor base 40 is mounted to a chassis 41 at three points C, D and E. At point C, the motor base 40 and the chassis 41 are connected together through a screw 42 with a spacer 44 sandwiched therebetween, whereby the motor base 40 is rendered capable of tilt actions at point C as a fulcrum in all directions. At point D, the chassis 41 and the motor base 40 are connected together via a screw 48 with a spring 46 sandwiched therebetween. In correspondence with the amount of screwing of the screw 48, the inclination angle of the motor base 40 is adjusted, using line F passing over points C and E as a tilt movement axis, in a direction around line F. At point E, the chassis 41 and the motor base 40 are connected together via a screw 52 with a spring 50 sandwiched therebetween. In correspondence with the depth or amount of screwing of the screw 5, the inclination angle of the motor base 40 is adjusted, using line G passing over points C and D as a tilt movement axis, in a direction around line G.
Japanese Patent Laid-Open Publication No. HEI-9-223353 discloses a still another conventional inclination angle adjusting mechanism as illustrated in FIG. 4 hereof. A spindle motor 53 includes a rotary shaft 54 to which a turntable 56 is mounted. The spindle motor 53 is fixedly disposed on a motor base 58. The motor base 58 is supported by a chassis 60 tiltably in all directions at point H. At point I, the chassis 60 and the motor base 58 are connected together by means of a screw 64 with a spring 62 sandwiched therebetween. In correspondence with the depth of threaded engagement of the screw 64, the inclination angle of the motor base 58 is adjusted, using a line passing over points H and J as a tilt movement axis, in a direction around the line or tilt movement axis. At point J. the chassis 60 and the motor base 58 are connected together by means of a screw 68 with a spring 66 sandwiched therebetween. In correspondence with the depth of screwing of the screw 68, the inclination angle of the motor base 58 is adjusted, using a line passing over points H and I as a tilt movement axis, in a direction around the line.
In the conventional inclination angle adjusting mechanism shown in FIG. 2, the height of the turntable 22 is influenced by a bend position error in the end portions 18a, 18b of the motor base 18 and positional and angular errors in the pedestal inclined surfaces 12a, 14a, thereby making it difficult to ensure precision of the height of the turntable 22. These positional and angular errors also reflect upon the track-tangential-direction position of the turntable 22, thus causing the direction of movement of the optical axis by the feed action of the optical pickup to be offset from a direction normal to a central axis of the optical disk. In addition, since a central axis of the tilt action of the eccentric cam 27 is imaginary, difficulty is experienced in establishing the axis at one point clearly.
In the conventional inclination angle adjusting mechanism shown in FIG. 3, since the motor base 40 vertically swings about point C the screws 48, 52 are turned, the turntable 38 vertically moves largely during inclination adjustment. There is therefore a problem such that focusing cannot be achieved where a displacement range of a focus actuator of the optical pickup is small. Further, as the screw 48 is turned, the motor base 40 tilts at the oblique tilt movement axis F passing over points C and E. This causes a tilt action to arise in both tangential and widthwise directions with respect to tracks of the optical disk, thus rendering the adjustment difficult to achieve.
In the prior inclination adjusting mechanism shown in FIG. 4, since the motor base 58 vertically swings about point H as the screws 64, 68 are turned, the turntable 56 vertically moves largely. As a result, focusing cannot be achieved where a displacement range of a focus actuator of the optical pickup is small.